Neurophysiological studies have shown that some neurons in the cortex in the superior temporal sulcus and the inferior temporal gyrus of macaque monkeys respond to faces. To determine if facial factors such as expression and identity are encoded independently by face-responsive neurons, 45 neurons were tested on a stimulus set depicting 3 monkeys with 3 expressions each. As tested on a two-way ANOVA, 15 neurons showed response differences to different identities independently of expression, and 9 neurons showed responses to different expessions independently of identity. Three neurons showed significant effects of both factors. Six of the neurons with responses related to expression responded primarily to calm faces, while 2 responded primarily to threat faces. Of a further set of 31 neurons tested on pairs of different expressions, 6 showed strong responses to open-mouth fear or threat expressions …